The present invention relates to a subharmonic mixer, i.e. a mixer operating with a local oscillator, whose frequency is half the frequency of a radio reception signal, with a view to carrying out the necessary frequency change prior to the amplification and detection of the signal to be processed in an EHF wave receiver.
It is known that it is possible to carry out the frequency change in an EHF wave receiver by using a symmetrical mixer which is placed in a waveguide carrying the signal to be received. An advantageous solution from the industrial standpoint is described in the U.S. Pat. No. 4,306,312, by the Applicant Company and in the Japanese Application No. 036035/80 filed on the same date. It involves the head to tail arrangement of two modules, each of which contains a detecting diode in the waveguide in which there is the electromagnetic field of the signal to be processed. The mixer is coupled to a waveguide at which discharges the local oscillator on the one hand and on the other hand to an amplifier of the beat frequency. The receiver having this amplifier has the advantage of being very sensitive to the signal to be received and relatively insensitive to the amplitude variations of the local oscillator. However, it has the disadvantages of requiring two waveguides, one for the signal to be processed and the other for the local signal making it necessary to use complex coupling means and of requiring a local oscillator at the same frequency as the signal to be received, which consequently becomes more onerous and less powerful as the frequency increases.